Draft inducing fan



May 16, 1961 cs. MCLARTY 2,984,407

DRAFT INDUCING FAN Filed Dec. 15, 1958 2 Sheets-Sheet 1 1817 r w I14INVENTOR.

--" eoavou MCLMZTY ATTO/ZA/EY May 16, 1961 G. MOLARTY DRAFT mnucmc FAN 2Sheets-Sheet 2 Filed D60. 15, 1958 INVENTOR. GORDON McLARTY BY W1 5ATTORNEY Uie DRAFT INDUCING FAN Gordon McLarty, 2600 Dickman Road,Battle Creek, Mich.

This invention relates to improvements in a draft inducing fan. Theprincipal objects of this invention are:

First, to provide a draft inducing fan which is durable and yetinexpensive due to reduced loads placed on the motor bearings as theresult of the method of mounting the fan and its motor.

Second, to provide a flue fan which can be adjusted to create differentdraft velocities in a flue but which utilizes an inexpensive one speedmotor. 7

Third, to provide an exhaust flue fan that can operate effectively inhot flues such as smoke pipes without detrimental effects from the heatand without resorting to expensive special heat resistant bearings andparts in the fan motor.

Fourth, to provide an exhaust fan mounting in a flue that provides amaximum efficiency or air flow in one position of the fan in the fluewithout creating an undue obstruction to natural draft air flow when thefan is not operating and in which the fan may be adjusted for any lesserdegree of induced draft including a negative or back draft if necessary.

Fifth, to provide a mounting for a draft fan and motor therefore thatpermits the motor to be mounted close to the fan and a flue in which thefan operates and which protects the motor from flue heat by establishingcooling air flow from around the motor through baffle plates into theflue.

Other objects and advantages of the invention will be apparent from aconsideration of the following description and claims. The drawings, ofwhich there are two sheets, illustrate a highly practical form of thefan assembly and three methods of mounting the same in a flue.

Fig. I is a fragmentary side elevational View of a portion of a smokepipe or flue with the draft fan of the invention mounted thereon.

Fig. 11 is a fragmentary cross sectional view taken along the plane ofthe line II-II in Fig. I.

Fig. III is a fragmentary cross sectional view showing a modified methodof installing the fan shown in Figs. I and II.

Fig. IV is a fragmentary enlarged cross sectional view taken along theplane of the line IV-IV in Fig. II.

Fig. V is an axial cross sectional view through second modified form offan mounting taken along a plane corresponding to the line VV in Fig.VI.

Fig. VI is an end elevational view of the flue and fan mounting shown inFig. V.

Fig. VII is an enlarged fragmentary cross sectional view taken along theplane of the line VIIVII in Fig. V.

Fig. VIII is a fragmentary axial cross sectional view through a thirdmodified form of fan mounting taken along the plane of the lineVIII-VIII in Fig. IX.

Fig. IX is a fragmentary end elevational view of the flue and fanmounting shown in Fig. VIII.

Fig. X is an enlarged fragmentary cross sectional View through the motormount connection in Fig. VIII and taken along the plane of the line X-X.

While the draft inducing fan of the invention is applicable to any fluesuch as an exhaust flue for stale air, it is particularly adaptable tofurnace exhaust flues or smoke pipes and will be described in thislatter relation. In Fig. I a smoke pipe is indicated in part at 1extending into a chimney 2. The draft inducing fan assembly indicatedgenerally at 3 is mounted on the side of the flue. It may be mounted onthe bottom of the flue but mounting on the top of the flue isobjectionable in that it subjetcs the motor to heat rising from theflue.

The fan assembly consists first of a mounting plate 4 that is generallyrectangular in outline but curved longit'udinally to fit against theside of the flue and close an opening 5 cut in the flue wall. The centerof the mounting plate is depressed or curved about an axis extendingtransverse to the flues and the depressed portion is cut away leaving anarrow flange 6 disposed generally along the surface of a segment of acylinder.

The opening within the flange 6 is closed by a first baffle plate 7secured to the flange by bolts 8. For cold ventilating flues the singlebaflie plate is suffiicient but for hot flues additional baifle plates 9and 10 are mounted on the first balfle plate by the bolts and spacingsleeves 12 that hold the baflie plates in spaced apart relation. Theright hand corners of the baffle plates 9 and 10 are slit to form anchortabs 13 that are bent into overlapping relation to receive the pivotbolts 14 disposed along a pivot axis transverse to the flue and locatedthereabove. The side arms 15 of a yoke 16 are adjustably secured to theanchors by the pivot bolts so that the transverse cross piece 17 of theyoke extends swingably across the right ends of the bafiie plates.

The cross piece 17 is bolted to the base 18 of a motor mount brackethaving end arms 19. that coact with clamps 2-0 to secure the ends of anelectrical motor 21 to the bracket. Rubber vibration dampening gnomrnets(not illustrated) may be mounted between the motor and the bracket andclamps. The axis of the motor is thus mounted in a longitudinal planethrough the center of the flue pipe 1 and is swingable in that plane.The shaft 22 of the motor projects generally radially through the batheplates 7, 9 and 10 to within the flue pipe. The baffle plates definearcuate slots 23 passing the shaft and permitting tilting adjustment ofthe shaft and motor about the pivot bolts 14. Fig. II illustrates themotor in full lines in inwardly tilted, maximum draft position and itwill be noted that in this position the motor 21 projects partially intothe cylindrical contour of the flue 1. The outwardly tilted minimum ornegative draft position of the motor and the shaft are indicated by thedotted lines at 21A and 22A respectively.

Secured to the end of the shaft within the flue is a screw typepropeller fan 24. In the inwardly tilted position of the motor 21 thefan tilts to a transverse inclined plane within the flue with its upperedge closely adjacent the inside of the flue. In this position it hasmaximum efliciency in creating a draft in the flue. When the motor isswung outwardly the fan swings to parallel or slightly oppositelyinclined position in the flue for zero or negative draft creatingability. It should be noted that due to the position of the pivot bolts14 outside the contour of the flue and offset from the shaft 22, the fanwill also swing outwardly away from the side of the flue opposite fromthe motor.

The inclined position of the fan 24 relative to the axis of the flue, inthe maximum draft position of the fan, causes the fan to present an ovalor elliptical surface to the transverse normally circular cross sectionof the pipe. In order to obtain maximum efficiency from the fan it isbest to close on the open area between the ellipse and the circle toprevent air from circulating back around the fan and to increase theefficiency of the fan. This can be done as shown in Fig. III by placinga stationary battle within the flue with its edge lying closely adjacent the ends of the fan blades in the inwardly tilted position of thefan. The baflle may be formed as a separate'metal plate or by anintegral portion of the wall of the flue pressed inwardly from thenormal cylindrical contour of the flue.

Fig. III also illustrates a modified assembly of the fan for insertioninto a flue. The mounting plate 4A is preassembled in a separate section1A of flue pipe to be assembled into a flue rather than cutting into anexisting flue and mounting the plate 1 thereover. Other possiblevariations include forming the mounting plate 4A as an integral part ofthe flue section 1A.

Figs. V, VI and VII show a second modified form of fan mounting. A hole26 of rectangular outline is cut into the flue 27. Mounted within thehole is an inner baflie 28 curved cylindrically about an axis inclinedinto the fine and closed at its inner end by an end Wall 29. Flanges 30on the ends of the baffle overlie the flue wall and support the baffle.Flanges 31 on the sides of the baflie support the sides. Within thebaffle 28 is a second smaller baffle 32 having an end wall 33 and endtabs 34 and side tabs 35. Bolts 36 secure the flanges 30 and 31 and tabs34 and to the flue and locate the batfles in spaced relation.

The side walls of the inner batfle 32 carry pivot bolts 37 whichswingably support the motor yoke 38. The yoke is secured at 39 to thebase bracket 40 of the motor 41. The motor is thus supported to swinginto the inner baflle with its shaft 42 inclined into the flue. Theshaft 42 passes through slots 43 and 44 provided therefore in the endwalls of the inner bafile and the outer baffle respectively. A screwpropeller 45 is mounted on the inner end of the shaft 42 to operate andto be adjusted as in the first forms of the invention described. Due tothe relatively narrow width of the hole 26 in the flue Wall, thepropeller 45 is desirably a two bladed propeller permitting its easyinsertion into the flue.

Figs. VIII to X illustrate a third modified form of fan mounting. Thefine 46 has a rectangular hole 47 cut in its side as in Figs. V to VII.An inner bafile 48 in the shape of the corner of a box fits into thehole. The bottom wall 49 has the end wall 50 folded therefrom andtriangular side walls 51 and 52 on the bottom and end walls respectivelyare folded into overlapping relation at the sides of the baffle. Theside walls are relatively bowed or offset as at 53 (see Fig. IX) to forma cooling passage between the walls into the flue. Angle strips 54secured along the outer sides of the side walls overlap the side edgesof the hole 47. An angle strip 55 having notches 56 in its dependingflange 57 is secured at its center as by welding at 58 to each end ofthe baffle and when the bafile is inserted in the hole the ends of thestrips are bent down around the curve of the flue to close the jointbetween the flue and the baflle.

An inner baflle 59 of the same configuration but smaller in size thanthe outer balfle 48 is mounted in spaced relation within the outerbatfle in spaced relation to the Walls thereof. A U-shaped bracket 60positioned between the side walls of the baffles at each side thereofspaces the baffles and is held in place by the pivot bolts 61 that alsoadjustably support the motor mounting yoke 62. As in the other forms ofthe fan assembly, the yoke 62 is connected at 63 to the mounting bracket64 of the motor 65. The motor shaft 66 extends through slots 67 in thebafiles to support and drive the screw propeller 68 in the flue.

The last two forms of the bafile insert into the flue shown in Figs. Vand VIII have a certain advantage in that they do not occupy andobstruct the entire chord of the flue and they can be formed by merelyfolding or rolling sheet metal. Thus they do not require dies andpresses for their formation. All forms of the bafile and fan mountprovide passages for cooling airto bedrawn around the'motor-andbetween-the-batfle plates through the slot that passes the motor shaft.The motor and shaft are thus cooled and the motor is shielded fromradiant heat of the flue. Due to the adjustability of the motor and fanan inexpensive standard single speed motor can be used to create thedesired draft in any flue depending upon the needs of the particularflue. The motor is close to the propeller and this reduces the effect ofvibration of the propeller on the motor bearings so no special bearingsare required. It should be noted that perfect balance of the fan isimpossible as soot collecting on the propeller will unbalance the bladeregardless of its initial balance so the matter of bearing loads becomesimportant.

What is claimed as new is:

1. A draft fan assembly for furnace flues comprising a mounting platecurved as a segment of a cylinder to fit a flue pipe and having anopening therein with a flange around the opening disposed along acylindrical surface transverse to said segment and intersecting the bendof the mounting plate to a substantial depth, a plurality of curvedbatfle plate secured in spaced relation with the lower plate secured tosaid flange to close said opening, ears turned from adjacent corners oftwo of said bafile plates into overlapping relation to form anchors attransversely opposite sides of said baflle plates, a yoke having theends of its arms adjustably pivoted to said anchors, an electric motorsecured to said yoke with its shaft extending generally radially throughsaid baffle plates and transverse to the line of said pivots andtherebelow, said baflle plates defining slots passing said shaft, and ascrew propeller fan on the lower end of said shaft having a diameterapproaching the diameter of the cylinder of said segment.

2. A draft fan assembly for furnace fiues comprising a mounting plate tofit a flue pipe and having an opening therein with a flange around theopening disposed along a cylindrical surface transverse to andintersecting the bend of the mounting plate to a substantial depth, aplurality of curved baflle plates secured in spaced relation with thelower plate secured to said flange to close said opening, anchors attransversely opposite sides of said baflle plates, a yoke having theends of its arms adjustably pivoted to said anchors, an electric motorsecured to said yoke with its shaft extending generally radially throughsaid bafiie plates and transverse to the line of said pivots, saidbalfle plates defining slots passing said shaft, and a screw propellerfan on the lower end of said shaft having a diameter approaching thediameter of the cylinder of said mounting plate.

3. A draft fan assembly for furnace flues comprising a mounting platecurved to fit a flue pipe and having an opening therein disposed along asurface curved transverse to and intersecting the bend of the mountingplate to a substantial depth, a curved baflle plate secured to saidmounting plate to close said opening, anchors at transversely oppositesides of said baffle plate, a yoke having the ends of its armsadjustably pivoted to said anchors, an electric motor secured to saidyoke with its shaft extending generally radially through said balfleplate and transverse to the line of said pivots, said balfle platedefining a slot passing said shaft, and a screw propeller fan on thelower end of said shaft having a diameter approaching the diameter ofthe curve of said mounting plate.

4. A draft fan assembly for furnace flues comprising a bafile plateshaped to fit within a fine pipe having an opening therein andintersecting the flue to a substantial depth, a second baffle platesecured in spaced relation within said first plate, anchors attransversely opposite sides of said plates, a yoke having the ends ofits arms adjustably pivoted to said anchors, an electric motor securedto said yoke with its shaft extending generally radially through saidbalfle plates and transverse to the line-of said pivots, said bafileplates defining slots passing said shaft, and a screw propeller fan onthe lower end of said shaft.

5. A draft fan assembly for a flue pipe and having an opening thereindisposed along a cylindrical surface comprising an outwardly openingchambered batfle positioned in said opening and intersecting the pipe toa substantial depth, anchors at opposite sides of said baflle having ayoke pivoted thereto and extending transversely of said pipe and thechamber of said baflle, an electric motor supported from said yoke andextending partially into the outline of said pipe with its shaftextending through said baffle in a longitudinal plane of the pipe andinclined relative to the pipe, said baflle plate defining an openingpassing said shaft, and a screw propeller fan on the lower end of saidshaft having a diameter approaching the diameter of the pipe.

6. A draft fan installation in a flue comprising a closure plate curvedabout an axis transverse to said line and projecting into the flue asubstantial distance to close an opening provided therefor in the flue,a heat shield plate mounted in generally parallel and spaced relation tosaid closure plate, an electric motor mounted partially within theconcave shape of said plates with its axis in a longitudinal plane ofsaid flue and with its shaft projecting into said flue, said platesdefining a slot passing said shaft, means pivotally adjustablysupporting said motor about an axis transverse to said flue and saidshaft and spaced from said shaft, and a screw propeller fan secured tothe end of said shaft within said flue, said flue having a flowrestricting baflie in its side opposite said plates conforming closelyto the periphery of said fan in the inwardly adjusted position of saidshaft and said fan with one tip of the fan closely adjacent the oppositeside of the flue from the baffle.

7. A draft fan installation in a flue comprising a closure plate curvedabout an axis transverse to said flue and projecting into the flue asubstantial distance to close an opening provided therefor in the flue,a heat shield plate mounted in generally parallel and spaced relation tosaid closure plate on the outer side thereof from said flue, an electricmotor mounted partially within the concave shape of said plates with itsaxis in a longitudinal plane of said flue and with its shaft projectinginto said flue, said plates defining a slot passing said shaft, meanspivotally adjustably supporting said motor about an axis transverse tosaid flue and said shaft and spaced from said shaft, and a screwpropeller fan secured to the end of said shaft within said flue.

8. A draft fan installation in a flue comprising a closure plate curvedabout an axis transverse to said flue and projecting into the flue asubstantial distance to close an opening provided therefor in the flue,an electric motor mounted partially within the concave shape of saidplate with its axis in a longitudinal plane of said flue and with itsshaft projecting into said flue, said plate defining a slot passing saidshaft, means pivotally adjustably supporting said motor about an axistransverse to said flue and said shaft, and a screw propeller fansecured to the end of said shaft within said flue, said flue having aflow restricting baflie in its side opposite said plate conformingclosely to the periphery of said fan in the inwardly adjusted positionof said shaft and said fan 6 with one tip of the fan closely adjacentthe opposite side of the flue from the baflie.

9. A draft fan installation in a flue comprising a first baffle platebent concavely outwardly relative to said flue and projecting into theflue a substantial distance to close an opening provided therefor in theflue, a second baflle plate angled concavely and supported in spacednested relation in said first baflle plate, an electric motor mountedpartially within the concave shape of said second plate with its axis ina longitudinal plane of said flue and with its shaft projecting intosaid flue, said plates defining slots passing said shaft, means.pivotally adjustably supporting said motor about an axis transverse tosaid flue, and a screw propeller fan secured to the end of said shaftwithin said flue.

10. A draft fan assembly adapted to fit in a rectangular opening in theside of a flue pipe comprising a first baflle having angularly disposedbottom and end walls, inner and outer triangular side walls folded fromthe adjacent edges of said bottom and end walls with the side walls ateach side "of the baffle in lapped relation and secured together attheir free edges but deflected and spaced apart to form air passageopening therebetween to said end wall, angled strips secured along theadjacent outer edges of said bottom, end and outer side walls to supportsaid baffle in said opening and close the joint between the baffle andthe flue, a second baffle shaped correspondingly to said first bafllebut being smaller than said first baffle, means supporting andconnecting said second baflie in spaced nested position within saidfirst bafie, a motor projecting into said second baflle in generallyparallel relation to the bottom thereof with the shaft of the motorprojecting through said end walls, said end walls defining openingspassing said shaft, and a screw propeller blade mounted on the end ofsaid shaft to operate in inclined position in said flue pipe.

11. A draft fan assembly adapted to fit in a rectangular opening in theside of a flue pipe comprising a baffle having angularly disposed bottomand end walls, inner and outer triangular side walls folded from theadjacent edges of said bottom and end walls with the side walls at eachside of the baflle in lapped relation and secured together at their freeedges but deflected and spaced apart to form air passages openingtherebetween to said end wall, angled strips secured along the adjacentouter edges of said bottom, end and outer side walls to support saidbaffle in said opening and close the joint between the bafile and theflue, a motor projecting into said baflie in generally parallel relationto the bottom thereof with the shaft of the motor projecting throughsaid end wall, said end wall defining an opening passing said shaft, anda screw propeller blade mounted on the end of said shaft to operate ininclined position in said flue pipe.

References Cited in the file of this patent UNITED STATES PATENTS1,182,863 T'oussaint May 9, 1916 1,707,281 Sauv-age Apr. 2, 19292,419,962 McLarty May 6, 1942 FOREIGN PATENTS 664,011 Great Britain Ian.2, 1952

